Electrical circuit arrangement



Feb.. Il, 1936.

fa 7b R. K. POTTER ELECTRICAL CIRCUIT ARRANGEMENT Original Filed Jan. 19, 1935 252 2 2 12,592 5571A; Zef 75 J2e 2b) 2ay [2d 29x 2 Sheets-Shea?l l lNVENTOR ATTORNEY Feb Ml, E936. R Kl POTTER Y ELECTRICAL CIRCUIT ARRANGEMENT Original Filed Jan. 19, 1953 2 Sheets-Sheet 2 INVENTOR @.Kffif BY L ATTORNEY Patented Feb. 11, 1936 UNITED STATES PATENT orties' ELECTRICAL CIRCUIT ARRANGEll/[ENT Ralph Kimball Potter, Madison, N. J., assignor to American Telephone and Telegraph Company, a corporation of New York Original application January 19, 1933, Serial No. 652,556. Divided and this application August 18, 1933, Serial No. 685,790

14 Claims. (Cl. 178-44) This application is a division of my application trates an inductance element in which the radius Serial No. 652,556, filed January 19,1933. of the enclosing vessel (assuming a hollow circu- This invention relates to an electrical induclar cylinder) is large in comparison with its tive element, adaptable to concentric conductor length. transmission lines, the physical dimensions of The manner in which the enclosing vessel func- 5 which are not necessarily related to the wave tions as an inductance will now be described in length of oscillation and in which the currents detail. The inductive device is illustrated in and potentials. may be distributed symmetrically Fig. 2. To the left of Fig. 2 is shown the equivaabout an axis. lent electrical circuit. This device consists of In the following description there is disclosed two concentric conductors I and 3 projecting into 10 in detail the functioning of this inductive device' a closed cylindrical vessel 2 of conducting material and arrangements of this inductive device in comwhich forms the reactive element. This cylindribination with capacitative and resistive elements cal vessel or tank, as it will henceforth be to form translation circuits such as so-called T called, is co-axial to the concentric system, the networks and Pi networks, the latter however, central conductor of which makes contact with 15 being'specically claimed in a divisional applithe center of the opposite face 20.' of the encation, closure, while the external conductor which pro- In the drawings, Fig. la illustrates a simple jects some distance into the tank is connected to concentric conductor circuit; Figs. 1b, 1c and 2 the near or left-hand face 2c. The size of this illustrate forms of the inductive device which is tank and the relative distance that this outer 20 used in connection with the present invention; COIldllCtOI, SeCtiOn 2d, Projects 11,1170 the tank are Figs. 3 to 6, inclusive, show translation circuits of the determining GC'GOTS 0f the amount 0f i11- the T type embodying the invention; Figs. 7 to 12, ductance obtainable from the tank circuit. inclusive, show translation circuits of Pi type em- The path that the radio-frequency currentv bodying the invention; Figs. 2 to l2', inclusive, takes in this circuit is as follows: Let it be as- 25 are simplined electrical diagrams showing the sumed that the Wave coming down the concentric equivalent electrical circuits of the various transconductor is such at the instant under discussion lating arrangements; and Figs. 2, 4", 5 and that current flows to the right on the inner con- 11 are end views to show the cross-sectional ductor l and to the left on the inner surface of form of the enclosing vessels. Also, Fig. 6" is a the outer conductor 3. When the current on I 30 longitudinal section corresponding to Fig. 6 but reaches the end of this conductor, it Will flow with more indication of structure, and Fig. 6 is outward along the face of the cylindrical ena cross-section on the line 6' of Fig. 6". closure 2a, then to the left on the inner side An important feature of the inductive element of the walls of the tank 2b, inward on the inner disclosed in this application is that its longiside of the left-hand face 2c, to the projecting 35 tudinal dimensions are not directly related to section of conductor 3, which is labeled 2d, to

the wave length of oscillation. Fig. lA illustrates the right along the outer surface of 2d to its end a section of concentric conductors short-circuited and thence to the inner surface of 3 and to the at the far end of a length L. It is readily apleft. The current flow has been indicated to some parent that the input impedance Z of this secextent in Fig. 6" and will be mentioned again in 40 tion is a function of the length as the constants that connection.

of the circuit are distributed smoothly along the The current which followed the path described circuit. In Fig. 1b. is shown the inductive eleabove, around the interior surfaces of the cymentof this invention, the functioning of which lindrical vessel, will be seen to have flowed as a will be described later in more detail. In this current sheet which formed the surface of some- 4.5 structure, the constants of the concentric conthing resembling atoroid. The magnetic field asductor circuit may be obtained in greater magnisociated with this current would consist of cirtude; thus the physical .dimensions of the encloscular lines of force lying Within the vessel, coning vessel, which is large in comparison with centric to the concentric tube conductor and cothe concentric conductors, may be so chosen as axial with it. It is evident that the inductive 50 to result in the input impedance Z being equal to effects of this current with its associated mag- Z, butv Z' is not necessarily a function of the netic field represent the inductive element of the physical length of the element (L'i). equivalent circuit.

The proportionality of the various dimensions It is also evident that there will be certainv of the inductive element is variable. Fig. 1c illusdistributed capacity effects in this structure, for 55 example, the capacity between the internal surface of the terminating vessel and the external surface of the concentric tube structure projecting into it. 'Ihese stray capacities will, in general, be of the same character as the distributed capacity in an ordinary inductance coil and will be minimized to the extent that the physical dimensions of the system are small in comparison with the wave length of the currents involved. Therefore, the exactness with which true capacities and true inductances can be simulated will be subject to the same diculties as are involved with ordinary coils and condensers, although they may be of a different order of magnitude.

While several ways of viewing the transfer of energy through the device of this invention are permissible, if one looks at the phenomenon in terms of a flow of current, then the action of the device may be understood more clearly by pointing out that the tank cylinder 2 and conductor l act eiectively as a one-turn toroid of rectangular cross-section in which, as previously stated, the current may be considered as entering on conductor l, spreading out radially over the remote disc end, passing longitudinally along the inner surface of 2, coming in radially on the inner surface of the other disc end, flowing on the outer surface of the portion 2d towards the right, and then flowing to the left on the inner surface of 2d and continuing on the inner surface of 3. This sets up a magnetic eld entirely enclosed in the tank and introduces an inductance the value of which can be obtained approximately from a wellknown formula for the inductance of a toroid of rectangular cross-section. Among other places, this formula is given in Bureau of Standards Circular No. 74, page 251, as:

in which L is expressed in microhenries, n is the number of turns (in this case, one), h is the inside length of the tank, r1 is the radus of the inside conductor and r2 is the inside radius of cylinder 2.

As an illustration, we may take h= centimeters, 1'1=.25 centimeters and r2=50 centimeters, whereupon calculation readily shows that L=1.06 microhenries. It will be evident from the formula that a wide Variety in the length and radial dimensions of the tank circuit will provide the same value of inductance L. Y

The extent toy which conductor 3 extends into the tank has an effect on the constants of the circuit, but precise formulae therefore are not available. In general, however, if one considers the transmission line as including the portion 2d and terminating at the end thereof, then the inductance of the tank circuit is approximately proportional to the area of the longitudinal crosssection of the tank reduced by the area of the longitudinal cross-section of the portion of the transmission line extending into the tank. Thus it is seen that lengthening the portion of the conductor 2d decreases the inductance of the device to a small extent. Another consideration in this connection, however, is the degree of coupling between the conductor I and the tank circuit. This coupling comes about chiey through the uncovered portion of conductor I within the tank and is -greater as the uncovered portion increases, that is, as the length 2d decreases.

It should be emphasized again that the use of the tank circuit is not dependent upon the frequency to be impressed upon the line and that, in fact, the value o1' the inductance, as calculated. will be substantially independent of frequency so long as the wave length corresponding thereto is large compared to the dimensions of the parts of the device. In certain cases, however, as in Figure 3b, some of the dimensions may approach those of the wave length or be simply related thereto, in which event certain special results are obtained.

The manner in which the principles above outlined are applied to T networks Will now be described. A simple T network consisting of resistance elements is illustrated in Fig. 3. Assume that the current ow at a particular instant is to the right on the inner conductor and to the left on the inner surface of the outer conductor. Current on la travels to the hollow cylindrical resistance 6 where part of it leaks across to the inner surface of the outer conductor where it passes to the left across the resistance I0a. The remaining portion continues to the right to the terminating circuits and on returning on 3b iiows across the resistance |017, then to 6 where it joins that portion which is iiowing through 6, thence across Illa and to the left along the inner surface of 3a.

In Fig, 4 the series resistances of Fig. 3 have been replaced by inductances. This arrangement is obtained by placing two tanks, illustrated in Fig. 2, back to back and continuing the central conductor through the two tanks. Current traveling to the right on la reaches the hollow cylindrical resistance 6, where part of it leaks across to the left-hand face of the central partition 2a, thence around the interior of tank 2A to the inner surface of the outer conductor 3a where it proceeds to the left. 'Ihe remainder of the current flows along Ib and returns on 3b, where it passes around the interior of tank 2B, by the way of 2e, 2g and 2h, thence to face 2a and around the interior of tank 2A with that portion of the current that is flowing across resistance 6.

In Fig. 5 the shunt resistance of Fig. 4 has been replaced by a condenser 1. This condenser is made by attaching a disc to conductor la near the central partition of the double tank. Part of the current which is assumed to be traveling to the right on conductor la passes through condenser 'l to ther face 2a as displacement current and along the interior of tank 2A and then to the left on the inner surface of conductor 3a. The remainder of the current travels along Ib to the terminating circuits and back along the inner surface of 3b, then around the interior of tank 2B to face 2a of tank 2A where it joins the current that is owing as displacement current through condenser 1.

Fig. 6 illustrates the manner in which resistances may be added in series with one side of the circuit. Resistance may be added in series with the inductances by inserting hollow cylindrical resistances in conductors 3a and 3b. The current flow in Fig. 6 may be much the same as in Figs. 4 and 5 as described above. It is indicated for Fig. 6 by the arrows in Fig. 6". It will be understood that at the high frequencies here involved the currents are not all in the same phase at different places along the vconcentric conductor system and the similarity of the arrows in Fig. 6 should not be taken to mean that the current is precisely in the same phase at all places where these arrows appear.

'I'he capacity adjustment which is indicated symbolically by the oblique arrows in Figs. 5 and 6 is indicated with more suggestion of structure in Figs. 6" and 6"'. The capacity 1 of Figs. 5 and 6 resides in the condenser having the outer spiral plate 1I and the corresponding inner spiral plate 12. The enclosing cylindrical vessel 2A2B has journal-bearing mountings on the shells 3a and 3b of the concentric conductor system, these journal-bearings being indicated at 13. By rotae tion of the shell 2A--2B around its axis by means of the handle 14, the radial spacing between the condenser plates 1| and 12 may be varied so as to adjust the capacity of the condenser as may be desired.

Arrangements of the elements of this invention to obtain Pi networks are illustrated in Figs. 7 to 12, inclusive. In Fig. 7 an arrangement consisting of an inductance in one side of a line with two resistances shunting the line, one each side of the inductance, is illustrated. This arrangement differs from that of Fig. 2 particularly in that the concentric conductor enters the enclosing vessel or tank 2 at each end wall thereof, the inner conductor, however, extending entirely through the tank. In Fig. '7 also, resistances 6a and 6b are added, which may be in the form of hollow cylinders enclosing the inner conductors la and Ib and extending to the outer conductor 3a or 3b as the case may be.

This arrangement functions as follows:

If the current is iiowing toward the right on conductor la, part of the current passes through the resistance 6a to the conductor 3a. Part of the current also ows over the inner conductor to the resistance 6b where it again divides, part of the current owing through the resistance 6b to the outer conductor 3b and part of the current passing over the inner conductor to some distant point and thence returning on the inner surface of the outer conductor 3b, where it joins with the current through the resistance 6b to flow to the inner end of the inner surface of the outer conductor 3b, and thence over the outer surface 2e, then over the inner surfaces 2a, 2b and 2c of the enclosing vessel or tank 2, thence over the outer surface 2d of the outer conductor 3a, and finally over the inner surface of the outer conductor 3a to join the current through the resistance 6a, which then flows on to the left on to the inner surface of the outerconductor 3o.

In Fig. 8 the shunt resistances of Fig. 7 have been replaced by shunt condensers. The condensers are formed by attaching flanges to the ends of the two sections of the outer conductors which project into the tank from opposite directions and by attaching a disc to the inner conductor .of the concentric conductor system, between these two flanges. Thus each side of the disc forms a plate for one of the condensers.

The operation of the arrangement in Fig. 8 is as follows: Current flowing to the right over conductor la divides at the disk associated with the inner conductor, part of the current flowing as a displacement current through the plates of the condenser 1a and thence over the inner surface of the outer conductor 3a to the left. Part of the current flows as a displacement current through the condenser 1b and over the outer surface 2e of the outer conductor 3b to the inner wall 2f of the tank 2. Part of the current also continues over the inner conductor lb to some distant point and returns over the inner surface of the outer conductor 3b to the end of said outer conductor near the center of the enclosing tank from which point it passes over the outer surface 2e of the outer conductor along with the displacement current previously described. From this point the displacement current and the returning current flow over the inner surfaces 2f, 2b and 2c of the tank 2, over the outer surface 2d of the outer conductor 3a, and then over the inner surface of the outer conductor 3a to the left.

Fig. 9 illustrates the manner in which resistance may be inserted in one side of the system. Resistances 5a and 5b are inserted in series with conductors la and Ib both sides of the central disc, the sides of which form the corresponding plates of the shunt condenser. Resistance could also be placed in the other side of the circuit by placing hollow cylindrical resistances in sections 3a and 3b of the outer conductor.

Fig. 10 illustrates the manner in which a series resistance may be placed in one side of the circuit between the two shunt condensers. In this arrangement it was necessary to spread the condensers and insert resistance 5. Thus two discs attached to the central conductor are required rather than one as in Figs. 8 and 9. Assume that the current in the system at a particular instant is traveling to the right on the inner conductor la. This current reaches the first disc which is part of condenser 1a and divides, part flowing through condenser 1a as displacement current and back to the left on the inner side of conductor 3a, the. remainder flowing around the disc and across resistance 5 to condenser 1b. Here again the current divi-des, part of it flowing as displacement current through condenser 1b, and through the inductance 2 by way of 2e, 2a, 2b, 2c and 2d, to the inner surface of the flange of condenser 1a where it joins the displacement current that is flowing through condenser 1a. The remaining portion flows along Ib to the terminating circuits and returns along 3b to the flange of condenser 1b. Her-e it joins the displacement current that is flowing through 1b and takes the path described above for that current.

Fig. 11 illustrates an arrangement including resistance in series with the inductance of the Pi network. These networks are in two sections, one each side of the point at which a shunt condenser is attached to that side. The inner and outer surfaces of the hollow cylindrical resist- -ances which are placed in the two sections of the outer conductors which project into the tank constitute the two independent sections of the resstance which is placed each side of the inductances and between whose two sections the shunt condenser is connected.

Referring to Fig. 11 and assuming that the direction of current flow at a particular instant is to the right on the inner conductor and to the left on the inner surface of the outer conductor, the various paths of the current of the system are as follows: Current flowing to the right on la reaches the common disc of condensers 1a and 1b. Part of this. current flows as displacement current from the left-hand face of the central disc to the flange of 1a, thence to the left along the inner surface of the hollow cylindrical resistance in the left-hand section of the outer conductor and along the inner surface of this outer conductor 3a. The inner surface of this resistance is designated Illa. rI'he remainder of the current ows around the disc to the righthand face and some of it passes as displacement current through condenser 1b while the remainder travels along Ib. The portion that passes through 1b will flow around the flange and to the right across the outer surface of the hollow cylindrical resistance situated in the right-hand section of the outer conductor which projects into the tank. This outer surface is designated Id. This portion of the current then passes through the inductance 2 by way of 2e, 2a, 2b, 2c and 2d, to the right across the outer surface of the hollow cylindrical resistance in the left-hand section of the outer conductor, designated Ic, part of this current penetrating to the inner surface la and part of it flowing around the ange of 'la Where it joins the displacement current that is flowing through 1a, and thence along ma and 30,. The portion of the current which continues along Ib goes to the terminating circuits and returns to the left along the inner surface of the outer conductor 3b. Part of this current penetrates through the resistance which is situated in the right-hand section .of the outer conductor to the outer surface Id while the remainder flows across the inner surface, designated Ido, to the nange of condenser lb where it joins the displacement current which is flowing through condenser 1b.

Fig. l2 illustrates the manner in which a resistance may be inserted in one side of the circuit opposite the inductance branch and between the shunting condensers. In this arrangement, as in the one illustrated in. Fig. l0, the two condensers la and 'Ib are spread apart and a resistance 5 inserted in the central conductor between the twocondensers.

Although in the above discussion the inductive element was described as a closed hollow cylindrical vessel, it is not intended that this application. be limited to this particular system. Any physical system which is symmetrical about an axis could be employed; for example, the enclosing vessel might actually be a toroidal shape rather than a section of a cylinder. The inductance of this tank circuit may be made variable by several methods. The distance that the outer conductor projects into the tank may bemade variable by having the tank slip along the outer conductor or by dividing this section of the conductor into two parts, one of which slides into the other. The length of the tank may also be made variable by dividing it into two parts one of which slides into the other.

In the above discussion` I have shown means of obtaining inductance, capacity and resistance in a 'concentric conductor system. I have also shown ho-w these elements can be combined to give translation circuits such as T networks and Pi networks. Numerous other circuits, obtainable by various arrangements of the elements of this invention, will be apparent toI those skilled in the art. A great many of the various filter combinations known to the transmission art can be obtained by proper combinations of the above circuits. These circuit elements may also be used in oscillator and amplier circuits.

What is claimed is:

1. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having inductive properties, said arrangement including a closed vessel enclosing and coaxial with a section of said conductor system, the outer conductor of said concentric conductor system being divided into ltwo parts entering the enclosing vessel at different points, the inner concentric conductor being electrically continuous through the vessel,

the length of the tank being substantially 1ndependent of the length of the electric Waves.

2. In a concentric conductor system in Which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having inductive properties, said arrangement including a closed vessel"` enclosing said conductor system, the outer conductor of said concentric conductor system being divided into two parts entering the enclosing vessel at diiferent points, the inner concentric conductor being electrically continuous through the vessel, an inner conductive partition within the vessel and connected to the outer wall of the Vessel, and means to permit wave transmission from the inner concentric conductor to said partition.

3. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having the electrical properties of a T network including series inductance in one sideof the circuit with an impedance bridged from an intermediate point of said inductance to the other side of said circuit, said arrangement including a closed vessel enclosing said conducto-r system, the outer conductor of said concentric conductor system being divided into two parts entering the enclosing vessel at different points, the inner concentricconductor being electrically continuous through the vessel, an inner conductive partition within the vessel and connected to the outer wall of the vessel,

and means to permit wave transmission` from the inner concentric conductor to said partition.

4. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having the electrical properties of a T network including series inductance in one side of the circuit with a resistance bridged from an intermediate point of said inductance to the other side of said circuit, said arrangement including a closed vessel enclosing said conductor system, the outer conductor of said concentric conductor system being divided into two parts entering the enclosing Vessel at diierent points, the inner concentric conductor being electrically continuous through the vessel, and a resistance element surrounding and in contact with said inner concentric conductor and electrically connected to the outer wall of said vessel.

5. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having the electrical properties of a T network including series inductance in one side of the circuit with a capacity ridged from an intermediate point of said inductance to the other side of said circuit, said arrangement including a closed vessel enclosing said conductor system, the outer conductor of said concentric conductor system being divided into two parts entering the enclosing vessel at different points, the inner concentric conductor being electrically continuous through the vessel, an inner conductive partition within the vessel and connected to the outer wall of the vessel, and a flange on said inner conductor parallel to and sufciently close to said partition to form therewith said bridged capacity.

6. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having the electrical properties of a T network including series inductance in one side of the circuit with a capacity bridged from an intermediate point of said inductance to the other side of said circuit, said arrangement including a closed vessel enclosing said conductor system, the outer conductor of said concentric conductor system being divided into two parts entering the enclosing vessel at different points, the inner concentric conductor being electrically continuous through the vessel, an inner conductive partition within the vessel and connected to the outer wall of the vessel, a flange on said inner conductor parallel to and suiiciently close to said partition to form therewith said bridged capacity, and a resistance in said inner concentric conductor.

7. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having inductive properties, said arrangement including a closed vessel enclosing said conductor system, the outer conductor of said concentric conductor system being divided into two parts entering the enclosing vessel at different points, the inner concentric conductor being electrically continuous through the vessel, and a flange-like member associated with one of said concentric conductors, said flange-like member being parallel to the end wall of said vessel and forming a capacity therewith.

8. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having inductive properties, said arrangement including a closed vesnel enclosing said conductor system, the outer conductor of said concentric conductor system being divided into two parts entering the enclosing vessel at different points, the inner concentric conductor being electrically continuous through the vessel, and a flange-like member associated with said inner concentric conductor, said iiange-like member being parallel to the end wall of said vessel and forming a capacity therewith.

9. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having the electrical properties of a series lumped inductance, said arrangement including a conductive enclosure concentrically surrounding the two concentric conductors, the ends of said enclosure being connected to the outer of said two concentric conductors, this last named within the enclosure, the length of said interruption being adjustable.

l0. In combination, a concentric conductor pair having its inner axial conductor continuous but having its outer shell conductor interrupted by a gap, and a coaxial cylindrical vessel around the gap and the outer conductors adjacent to the gap, said vessel having annular end walls closed against said outer conductors, the interrupted ends of said outer conductors projecting equally into the coaxial cylindrical vessel.

11. In combination, a concentric conductor pair having its inner axial conductor extending continuously but its outer shell conductor being interrupted to form a gap, and means surrounding said gap and the adjacent parts of the outer conductor to form an equivalent interposed inductance in said outer conductor, the length of the gap being adjustable.

12. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having the electrical properties of a T or a Pi network, said arrangement including a conductive enclosure concentrically surrounding the two concentric conductors, the ends of said enclosure being connected to the outer of said two conductors, this last-named conductor being interrupted within the enclosure, the `said interrupted ends having anges to form elements of capacities.

13. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having the electrical properties of a T or a Pi network, said arrangement including a conductive enclosure concentrically surrounding the twoconcentric conductors, the ends of said enclosure being connected to the outer of said two conductors, this last-named conducto-r being interrupted within the enclosure, the interrupted ends and the inner conductor having attached elements acting as lumped impedances to give the assemblage the characteristic of a T or a Pi network.

14. In a concentric conductor system in which an inner conductor is surrounded by a cylindrical conductor concentric therewith and acting as a return therefor, an electrical arrangement for association therewith and having the electrical properties oi a T or a Pi network, said arrangement including a conductive enclosure concentrically surrounding the two concentric conductors, the ends of said enclosure being connected to the outer of said two conductors, this last-named conductor being interrupted within the enclosure, at least one of the three aforesaid conductors having attached to it a flange to give the system the characteristics of a T or a Pi network.

RALPH KIMBALL POTTER.

conductor being interrupted 

